The present invention relates to a technique for recording digital signals such as BS digital broadcasting signals.
From the end of 2000, full-scale Broadcasting Satellite (BS) digital broadcasting has been begun, and the market is filled with expectations of high resolutions to be televised in BS digital broadcasting. At the same time, the need of a digital video tape recorder (hereinafter referred to as a digital VTR) which can record BS digital TV programs with their high resolutions left intact is increasing.
Now, a video recording apparatus which has been proposed to date will be described. FIG. 4 is a block diagram showing the configuration of a conventional video recording apparatus 40. Video recording apparatus 40 comprises a digital signal receiving section 41, digital signal recording section 42, operating section 43, and recording rate detecting section 44.
Composing elements of video recording apparatus 40 are specifically described. Digital signal receiving section 41 receives digital signals containing video information, audio information, and channel information from the outside. Recording rate detecting section 44 detects the recording rate based on the digital signals inputted from digital signal receiving section 41. xe2x80x9cRecording ratexe2x80x9d means speed to record the digital signals, which has a same meaning of the receiving speed of digital signals and of transmitting speed of the digital signals transmitted from the broadcasting station. Operating section 43 receives commands such as recording rate, start of recording, stopping from the user for digital signal recording section 42. Digital signal recording section 42 records, in the recording medium, the digital signal inputted from digital signal receiving section 41 based on the recording rate detected by the recording rate detecting section 44 and commands from operating section 43.
The broadcasting station can insert the information of maximum bit rate of the TV program for each program with respect to the digital signals of BS digital broadcasting. Whether to insert or not is at the option of the broadcasting station.
Based on these, the operation of video recording apparatus 40 will be described. First of all, when digital signal receiving section 41 is connected to the digital signal output of the digital tuner, digital signal receiving section 41 sends the inputted digital signal to digital signal recording section 42 and recording rate detecting section 44. Recording rate detecting section 44 detects the information if the information concerning the maximum bit rate is included in the inputted digital signal and detects the recording rate based on the detection results. The detection results are sent to digital signal recording section 42. Or when the user operates operating section 43 to set the recording rate to the automatic mode, operating section 43 transmits the setting to digital signal recording section 42.
Once the recording rate is set, the user times the start of the TV program he/she wants to record, operates operating section 43, and sends the recording start command to digital signal recording section 42. Digital signal recording section 42 begins digital recording at the recording rate instructed by recording rate detecting section 44 in conformity to the commands of the operating section.
In the case in which a specific recording rate is not set, recording rate detecting section 44 detects the speed of the digital signals received, and based on the detection, decides the recording rate. Consequently, when the receiving rate of the digital signal varies during recording, the recording must be temporarily stopped, the recording rate must be changed, and then, recording must be started. Alternatively, operating speed of the recording medium (e.g. rotating speed of a magnetic tape) must be changed, which corresponds to the recording rate, and the recording must be continued. With this sort of operation, every time the recording rate is changed, the TV program in recording is interrupted, and for the user, this phenomenon results in nuisance to see and is extremely unpleasant.
It is an object of the present invention to record the digital signals with their high resolutions maintained and suppress the disturbance of reproduced video and/or audio associated with changes of recording rate of digital signals to the minimum.
To achieve the above objects, a digital signal recording apparatus for recording a digital signal having a variable recording rate representing a recording speed, said apparatus comprises a receiving section which receives the digital signal; a recording rate detecting section which detects the recording rate of the digital signal received at the receiving section; a storage section which stores a detected recording rate when said detected recording rate is greater than a previously stored recording rate, whereby said storage section stores a maximum recording rate; and a recording section which is operable to record the digital signal in a recording medium based on the maximum recording rate stored in the storage section.
The storage section holds the maximum recording rate when the recording rate detected by the recording rate detecting section is less than the maximum recording rate.
The digital signal recording apparatus further comprises an operating section which enters, in response to a user""s operation, a start command for starting recording of the digital signal and a stop command for stopping recording. The storage section may be reset in response to said start command, whereby the maximum recording rate is initialized.
The digital signal contains channel information for identifying the broadcasting station that transmits the digital signal and said receiving section detects changes of the channel information, and the storage section may be reset to the maximum recording rate when the receiving section detects a change in the channel information.
The digital signal may include a video signal and/or an audio signal.
To achieve the above objects, a digital signal recording method for recording a digital signal having a variable recording rate representing a recording speed, said method comprising: receiving a digital signal; detecting the recording rate of the digital signal received; storing a detected recording rate when said detected recording rate is greater than a previously stored recording rate, whereby the stored detected recording rate is a maximum recording rate; and recording the digital signal in a recording medium based on the maximum recording rate.
According to the present invention, a digital signal are recorded with the recording rate changed to a higher value only when the recording rate becomes higher than the previous recording rate and when the recording rate becomes lower than the previous recording rate, recording is continued without changing the recording rate. Thus, the frequency of interruptions of videos and/or voices caused by changes of the recording rate can be kept to minimum at the time of reproduction.